When cancer is suspected on an organ such as a breast, prostate, kidney or liver, a common diagnostic tool is to take biopsies of the organ tissue. A cancer may only be present in a very small portion of the organ in the early stages of its growth. However, this generally represents the stage when it is most desirable to detect the cancer. Cancer may also be uncorrelated and therefore may be present in a very small portion of the organ but at multiple places. Therefore the decision of where in the organ to take a biopsy will have a significant impact on successful early detection of a cancer as well as increasing the confidence of a negative result.
Maximum confidence in a biopsy outcome is currently only possible if the organ has been sampled at a multitude of locations. This technique is known as saturation biopsy and the number of core sites can reach 90 or more. Such saturation biopsy often causes considerable discomfort to the patient. Further, smaller organs such a prostate, which may only be 4 cm in diameter, may be damaged by sampling at numerous biopsy sites required for a saturation biopsy. However, as the number of biopsy sites decreases, so does the probability of an accurate result.
Management of biopsy targets is critical to a successful procedure. The operator must be able to plan each biopsy core site location, be able to accurately navigate the needle to each site to take the biopsy and finally to record the actual location of the biopsy site for future reference. This becomes overwhelming when a large number of sites are used. When a patient returns for multiple repeat visits the amount of data and complexity is increased proportionally.
Past biopsy data is also important to the planning process. An operator may not want to take a biopsy from a location that has already been biopsied and instead would like to sample from another region of the organ. Alternatively, due to a pathology report, a past site may now have a level of increased interest. The accuracy of site location is extremely important, especially when dealing with small organs. Taking a biopsy from a wrong location (so called false positive) can lead to injury and/or missed or incorrect diagnosis.
Visualizing where the biopsy sites will be located on the organ presents a challenge, especially when they are in large numbers. Complicating matters further is the fact that a biopsy site is actually a core sample in the shape of a cylinder. In the case of a prostate, the biopsy sites can become extremely dense and hard to visualize.